Too much of anything is a bad thing, and skepticism is no exception. Indeed, without some degree of trust, modern society would be impossible. Which brings us to another of those questions that dominated last weekend’s North Carolina Science Blogging Conference: Just what are bloggers good for, anyway?

Thousands of years back, long before the advent of toll-free product help lines, the typical member of Homo sapiens was entirely capable of evaluating the advice and opinions of their family, friends and hunting-party colleagues. Most knowledge was essential, and therefore shared by all members of a community. Specialized expertise was non-existent. Skepticism was warranted only when the source was a stranger whose motives were unknown.

Today it is nearly impossible to function without leaving many critical issues to the “experts.” You should be skeptical of those without public reputations or decent references, but sooner or later you have to trust a mechanic, plumber, or physician. You have to do this because it is impractical to develop the skills and knowledge required of a responsible and engaged 21st century citizen. “Trust no one” makes for a fine motto if you’re Fox Mulder. But in the real world, it would be suicide.

So it is with public policy challenges such as climate change. We can’t all afford to take a decade-long break from whatever it is that keeps the rent paid to get a PhD in earth sciences, so we let those who choose to devote their lives to the subject tell us whether the planet’s climate is in a state of predictable equilibrium or poised on the precipice of a dramatic regime shift that will require a radical reorganization of civilization’s economic and industrial foundations.

When we hear that skepticism is a useful intellectual tool, but are then asked to put our trust in a team of climatologists, what should we do? If the issue was a malfunctioning car, the answer would be obvious. One strange mechanic’s opinion that the problem will cost $8,000 to fix should be treated with a fair degree of skepticism. But if three or four mechanics from independent shops all offer you an estimate of $3,000 to repair the same identified failure, it simply makes no sense to keep shopping around for someone who will assure you that a $9 part is sufficient.

Similarly, when a retired geography professor who hasn’t published a peer-reviewed paper on climate science since before Bill Clinton had to worry about definitions of sex tell us that there’s nothing to worry about, while several thousand practicing climatologists warn us that fossil-fuel emissions are warming the planet and that we are rapidly approaching the aforementioned precipice, whom are we to trust?

For anyone with even a cursory respect for the scientific process, its skeptical foundations, intrinsic resistance to extremism and self-correcting mechanisms, this is the proverbial no-brainer. We simply ask ourselves: “How likely is it that an entire field of scientific expertise is going to be so completely wrong about basic scientific principles?”

But given that many retired professors are still relatively wise, that a lack of recent peer-reviewed publications doesn’t necessarily mean one has lost all connection to reality, and science never supplies absolute guarantees of rock-solid predictions about anything, this kind of question can pose a problem for those less familiar with science but still making a sincere attempt to be responsible and engaged citizens.

Enter the bloggers, many of whom have stepped into the critical role of offering a way to evaluate the trustworthiness of the experts. Over at Tim Lambert’s Deltoid science blog, we are treated to concise evaluation of the competence of one Tim Ball, a Canadian climate change pseudoskeptic who has become the darling of those who believe the climatology gang simply doesn’t understand the first thing about their chosen field.

Ball, we learn, recently wrote a letter to an editor in which he recalls how at a public presentation, he

posed the question about what happens to the water level when an ice cube is placed in a glass which is then filled to the brim and the ice melts. The correct answer is the water level drops because the space occupied by the ice is greater than that occupied by the water it contains. Water expands when it freezes.

Thereby demonstrating his misunderstanding of a fundamental physical phenomenon —;;;;; the Archimedes principle —;;;;; and fatally underming any credibility he may have previously enjoyed as an expert on the fate of the Earth’s ice caps.

Tim succinctly points out that “The extra space that the frozen water takes up is, by Archimedes principle, exactly the volume that sticks out of the water. So the water level doesn’t change.” It is possible to get distracted by ancillary issues, like salinity and the elevation of the interior of Greenland, but when the all relevant factors have been considered the essential fact remains that when the Greenland and Antarctic ice caps melt, the sea level will rise, not drop.

It’s this combination of genuine expertise, ability to write plainly, abundant good will and, most importantly, the spare time to freely contribute, that makes bloggers increasingly valuable players in public conversations. They help us figure out whom to trust and when to exercise some of that invaluable skepticism

One might wonder if that just begs the question of which bloggers to trust. But thanks to the hyper-linked nature of the internet and ease with which an amateur can verify, track down and judge the assertions of bloggers, that isn’t really a challenge.

Of course, this hasn’t stopped nonsensical conspiracy theories, reactionary historical revisionism and outright lies from propagating far and wide through the net. But for those actually interested in searching the truth, rather than mere rationalizations of pre-existing biases, the blogosphere has become an essential element of the process. And I can think of no better example than scienceblogs.com, of which I am honored to be small part.

“But if three or four mechanics from independent shops all offer you an estimate of $3,000 to repair the same identified failure, it simply makes no sense to keep shopping around for someone who will assure you that a $9 part is sufficient.”

But sometimes a $9 part takes $2991 in labor… Maybe the solution is cheap but expensive to implement? Blogging lowers the costs of labor, but who are our customers?